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Seeed’s “ReSpeaker 4-Mic Array for Raspberry Pi” add-on has 4x mics and a 12-LED ring to offer Echo-like voice detection and directional capabilities.
There are an increasing number of software solutions available for adding voice agent technology to the Raspberry Pi, including options for the Alexa agent found on the Amazon Echo, the Google Assistant technology available on Google Home, and even IBM Watson voice services. Yet, typical microphone add-on boards are often not up to the task of accurate voice detection especially in multi-speaker environments. Seeed Studios has a solution in the form of a $24.90 ReSpeaker 4-Mic Array for Raspberry Pi.

Respeaker 4-Mic Array on a Raspberry Pi
(click images to enlarge)

The ReSpeaker 4-Mic Array follows up on Seeed’s $9.90, dual-microphone ReSpeaker 2-Mics Pi HAT. The new add-on board doubles the number of microphones and offers an improved ADC. The quad-mic array also provides a 12-LED ring for indicating the direction of the speaker in voice-activated applications.

Respeaker 4-Mic Array, top and bottom
(click images to enlarge)

The Respeaker 4-Mic Array is equipped with a quad-channel AC108 [translated] ADC from Chinese firm X-Powers. The AC108 features a 108 dB dynamic range at ADC rates between 8kHz and 24kHz, and offers integrated I2S/TDM output transition circuitry for high definition voice capture.

Respeaker 4-Mic Array detail view
(click image to enlarge)

The add-on board also provides an LED ring made up of 12x APA102 LEDs that can light up to indicate the location of the voice the agent is conversing with. The result is a Raspberry Pi that can “do VAD (Voice Activity Detection), estimate DOA (Direction of Arrival), and show the direction via LED ring, just like Amazon Echo or Google Home,” says Seeed. KWS (keyword search) is also available.

Dual-mic ReSpeaker 2-Mics Pi HAT
(click image to enlarge)

The Respeaker 4-Mic Array’s four analog mics support voice recognition at up to three meters. The 65 x 65 x 9mm, 20-gram device does not handle voice output, but you can use the Pi’s headphone jack for output. A pair of Seeed Grove interfaces is also onboard.

The device supports the Raspberry Pi B+, 2, 3, Zero, and Zero W boards, and schematics are also available. Since the new AC108 is not yet support in the Pi kernel, you must set up the driver manually. Seeed provides instructions, including how to add an alsa plugin for decoding data, and how to test the solution using Open Audacity.

Matrix Voice

Matrix Voice and Conexant AudioSmart 2-mic

For a higher-end microphone add-on for the Raspberry Pi, you can check out Matrix Labs’s 7-microphone Matrix Voice, which funded on Indiegogo earlier this year, and is now available for $55. Matrix Labs went on to launch a Kickstarter campaign for a slightly enhanced version, but on Aug. 15, Kickstarter pulled the plug on the project due to the fact it had been previously crowdfunded on Indiegogo. Matrix Labs cried foul, suggesting Kickstarter should have allowed the project to fund or should have denied permission in the first place. In any case, all new orders made on Indiegogo will get the enhanced version starting in October, says the company.

Another high-end option for Alexa Voice Service is the Conexant/Amazon AudioSmart 2-mic Development Kit for the Raspberry Pi 3. The $299 product only has two mics, but it features dual high dynamic range ADCs and a Conexant AudioSmart CX20921 Hands-free Voice Input Processor configured with Alexa “wake word” technology.

Further information

The Respeaker 4-Mic Array is now on sale for $24.90, with volume discounts available. More information may be found on Seeed Studio’s Respeaker 4-Mic Array shopping and wiki pages.